Photographic compositions, products and processes



Oct. 3, 1967 M. GREEN PROCESSING COMPOSITING COMPRISINGI ITO 7% LITHIUM HYDROXIDE-,O.25 T0 |5% CARBON BLACK;

I TO 8% OF A p-AMINOPHENOL; AND A SILVER PHOTOGRAPHIC COMPOSITIONS, PRODUCTS AND PROCESSES Filed April 27, 1964 OPAQUE SUPPORT LAYER PHOTOSENSITIVE GELATINO SILVER HALIDE EMULSION LAYER HALIDE SOLVENT IMAGE-RECEIVING LAYER COMPRISING A SILICEOUS MATRIX INCLUDING SILVER PRECIPITATING AGENTS OPAQUE SUPPORT LAYER INVENTOR.

ATTORNEYS United States Patent 3,345,167 PHOTOGRAPHIC COMPOSITIONS, PRODUCTS AND PROCESSES Milton Green, Newton, Mass, assignor to Polaroid Corporation, Cambridge, Mass, a corporation of Delaware Filed Apr. 27, 1964, Ser. No. 362,620 19 Claims. (Cl. 9629) The present invention relates to photography and, more particularly, to compositions and products particularly adapted for employment in silver diffusion transfer processes.

In diffusion transfer processes, for the formation of positive silver images, a latent image contained in a selectively photoexposed photosensitive silver halide emulsion is developed. Almost concurrently therewith, a soluble silver complex is obtained by reaction of a silver halide solvent with the unexposed and undeveloped silver halide of said emulsion. Preferably, the photosensitive silver halide emulsion is developed with a processing composition in a viscous condition, which is spread between the photosensitive element comprising the silver halide emulsion and a print-receiving element comprising, preferably, a suitable silver precipitating layer. The processing composition effects development of the latent image in the emulsion and substantially contemporaneous therewith forms a soluble silver complex, for example, a thiosulfate or thiocyanate complex, with undeveloped silver halide. This soluble silver complex is, at least in part, transported in the direction of the print-receiving element and the silver thereof is largely precipitated in the silver precipitating layer of said element to form the desired positive image therein.

High speed diffusion transfer processes are generally the type in which, for example, a silver halide stratum containing a latent image formed at a low exposure level and an image-receiving stratum, in superposition, are subjected to a processing composition containing a highly energetic silver halide developing agent and a silver halide solvent in order to form a silver transfer print in and/ or on the image-receiving stratum. The silver halide developing agent serves to reduce the photoexposed silver halide to silver in the photosensitive emulsion stratum. The silver halide solvent reacts with unreduced silver halide to form the aforementioned soluble silver complex which, in turn, is reduced in the presence of the image-receiving stratum to form the desired positive print. The photosensitive stratum may be subsequently dissociated from the image-receiving stratum. Thus, the silver halide stratum may be underexposed in relation to its rated A.S.A. exposure index and the silver halide developing agent is specifically selected in order to provide the desired results. Preferably, the image-receiving stratum employed is one which will cause silver reduced there, in comparison with silver reduced in the photosensitive silver halide stratum, to possess high covering power, that is, opacity per given mass of reduced silver. This high covering power is achieved by accumulating the silver deposited in the silver-receptive stratum in unusually .dense masses, for example, by minimizing the thickness of stratum in which the silver-receptive material is contained.

As stated above, in one process of the aforementioned type, the processing composition is spread between a pair of opposed sheets to provide a stratum 0.001 to 0.005 of an inch thick, one of which carries the photosensitive stratum and one of which carries the photoinsensitive print-receiving stratum, and which may be characterized as a sandwich. Thereafter, the sheets are maintained in superposed relationship for a predetermined processing period during which the visible transfer silver print is provided to the photoinsensitive image-receiving stratum. At the completion of this processing period, the sheets are generally stripped apart to reveal the positive silver transfer image. Traditionally, this sandwich, during processing, has been kept in an actinic radiation proof chamber and thus insulated from exposure to extraneous actinic radiation, in order to prevent further exposure of the photosensitive stratum, prior to completion of the processing period. Recently, however, the introduction of self-developing film pack type cameras, such as those forming the subject matter of U.S. Patent No. 2,991,702, has given rise to extensive utilization of systems for effecting processing of photoexposed silver diffusion transfer film units external a radiation insulating chamber, and the problems incident with such systems. Camera apparatus of the general type disclosed in the cited patent permit successive exposure of individual film units including, in combination, a photosensitive element positioned for exposure within the camera, a second nonphotosensitive print-receiving element adapted to the superposed with the photosensitive element, during withdrawal of the film unit from the camera, following exposure, and a frangible container particularly adapted to releasably retain a fluid processing composition for distribution between the superposed photosensitive and print-receiving elements, subsequent to photoexposure of the film unit. As disclosed in the cited patent, the film assembly is designed, for at least the time interval necessary to effect transfer processing, to exclude impingement of incident actinic energy on the photosensitive component of the photosensitive element during, and subsequent to, withdrawal of the film assembly, from the camera, between, for example, a pair of pressure rollers adapted to effect rupture of the frangible container and distribution of the retained fi-uid processing composition between, and in contact with, the exposed photosensitive element and contiguous image-receiving element.

Accordingly, objects of the present invention are to provide novel compositions and products particularly adapted for employment in photographic silver diffusion transfer processes and, in particular, compositions and products particularly adapted to provide improved silver diffusion transfer processes, including high speed processes, wherein a selectively photoexposed silver halide emulsion is ex-,

posed within a camera device and adapted to be effectively processed, at least in part, without the actinic radiation insulated chamber of such device.

Other objects of the invention will be in part be obvious and will in part appear hereinafter.

The invention accordingly comprises the process involving the several steps and the relation and order of one or more of such steps with respect to each of the others, and the products and compositions possessing the features, properties and the relation of elements which are exemplified in the following detailed disclosure, and

the scope of the application of which will be indicated in the claims.

For a fuller understanding of the nature and objects of the present invention reference should be had to the following detailed description taken in conjunction with the accompanying drawing wherein:

FIGURE 1 is a diagrammatic enlarged cross-sectional view illustrating the association if elements during one stage of the performance of a diffusion transfer process, for the production of positive silver prints, the thickness of the various materials being exaggerated.

It has now quite unexpectedly been found that silver diffusion transfer processes of the aforementioned type may be improved by the employment of a diffusion transfer processing composition which comprises, in combination, an aqueous solution, preferably having a pH in excess of about 12, and including about 1 to 7% by weight,

lithium hydroxide, 0.25 to by weight, carbon black, and a silver halide developing agent, and preferably, additionally including about 1 to 8%, by weight, of a p-aminophenol silver halide developing agent and a silver halide solvent, distributed between a selectively exposed photosensitive emulsion stratum and a superposed image-receiving element having an image-receptive stratum comprising a silica matrix, preferably from 1 to 8 microns thick, incorporating silver precipitating agents.

As disclosed in the prior art, it is necessary that the diffusion transfer film unit, subjected to processing in an environment where actinic radiation is present, must be constructed such as to exclude radiation incident on the photosensitive emulsion, for at least the time interval necessary to effect substantial transfer processing of such film unit. As disclosed in the art, in general, the photosensitive element and the image-receiving element have traditionally been made nonresponsive to image-contaminating radiation, for example, by employment of actinic radiation opaque supports, for both the photosensitive emulsion layer and the image-receptive layer of respective elements, insulating the photosensitive emulsion during transfer processing. Alternatively, opaque layers or coatings have been mounted on, or affixed to, each support so as to effectively prevent penetration of actinic radiation to such extent as to engage, contact or contaminate the photosensitive emulsion stratum during the aforementioned transfer processing. To prevent entry of actinic radiation laterally through the edges of the described film unit during processing, the processing composition, distributed intermediate the photosensitive and image-receiving elements, has been disclosed to preferably contain an opacifying agent. One extremely effective and desirable type of opacifying agent comprises commercially available carbon black dispersed in the processing formulation.

As disclosed in US. Patent No. 2,698,237, a particularly desirable vehicle or matrix for constituting an imagereceptive layer containing silver precipitating agents comprises a macroscopically continuous film that consists of submacroscopic agglomerates of minute particles of waterinsoluble, inorganic siliceous materials such as silica aerogel. The use of such a vehicle or matrix for the precipitating agents tends to aggregate the silver that is precipitated into its most effective condition for silver print formation.

However, it has been found that the employment of carbon black, at least in the concentration necessary to provide an effective opacifying condition, and especially in the concentrations required where the image-receiving element does not of itself possess sufiicient opacity to transverse radiation, in silver diffusion transfer processes employing the aforementioned siliceous image-receiving vehicle, provides certain undesirable properties. Specifically, it has been found that transfer processing compositions containing carbon black, the specified adjuncts, and sodium and/or potassium hydroxide appear to possess an affinity for an image-receiving layer comprising a siliceous vehicle, in the presence of the silver precipitated therein to form the positive silver print. This affinity effectively causes the discontinuous retention of carbon black containing composition in intimate contact with the imagereceiving element, upon separation from the remainder of the film unit, subsequent to transfer processing. However, the adhesive bond between the carbon black retaining composition and the specified sections of the image-receiving stratum, while sufficient to prevent effective and clean separation of the positive print from the processing composition, does not possess such a capacity as to maintain the remaining carbon black retaining composition in continuous intimate contact with the print-receiving element. There is thus available a generally discontinuous deposit of processing composition which readily contaminates the person and effects of the individual or article upon which the disassociated positive print enters into contact. In addition to the effects of processing composition contact with such object, such contact further distributes the incidence of carbon black on a print-receiving element with a resultant detriment to positive image picture quality.

It has now been unexpectedly found that the employment, in silver diffusion transfer processes, of the processing composition detailed hereinbefore specifically overcomes the aforementioned disadvantages occasioned by the employment of the individual components specified. It has been found that the employment of lithium hydroxide as a replacement for the conventional employment of sodium and potassium hydroxides overcomes the disadvantages detailed above. Although the theoretical and/ or actual reasons for the effectiveness of the designated processing composition are not understood, it will be recognized that the lithium atom hydrates more extensively in solution than the corresponding sodium and potassium atoms, whereby the resultant hydrated lithium ions size may itself be sufficient to decrease penetration of the reception element and adhesion between the described processing composition and the silica matrix. Irrespective of the validity of this theory, it has specifically been found that employment of the present inventions processing composition does, as detailed herein, provide for the efficacious employment of carbon black, as an opacifying agent, in combination with a silica matrix and a p-aminophenol silver halide developing agent, in silver dffusion transfer processes.

The processing composition is of particularly desired characteristics for employment in high speed transfer processes where, because of the film units high degree of light resonsive sensitivity, an opacifying agent having the effective properties of carbon black is required in combination with a highly energetic silver halide developing agent such as certain p-aminophenols disclosed in the art and, preferably, in further combination with an imagereceiving stratum formulated such as to cause the precipitated image-silver to possess high covering power, for example, those reception elements comprising a silica matrix incorporating silver precipitating agents.

It will be recognized from the foregoing explanation that the lithium ion component may, where desired, be provided by employment of lithium salts other than the stated hydroxide, for example, lithium nitrate, chloride, sulfate, carbonate, etc. However, the employment of lithium hydroxide is preferred in that it directly contributes to the attainment and maintenance of the compositions preferred alkaline pH.

Where desired, the lithium hydroxide may be in part replaced by conventional sodium and potassium hydroxides, with a consequent reduction in the detailed specific advantages, as the concentration of the sodium or potassium hydroxides increases.

The preferred diffusion transfer processing compositions, particularly adapted for employment in the disclosed processes, additionally contain a film-forming material such as a Water-soluble plastic having a viscosity from 1,000 to 200,000 cps., at a temperature of 20 C., in order to permit the solution to be readily controlled during and after spreading. A preferred film-forming and viscosity-increasing agent is a high molecular weight polymer such as a polymeric, Water-soluble ether which is inert to an alkaline solution such as a cellulose ether, for example, sodium carboxymethyl cellulose or a hydroxyalkyl cellulose such as hydroxyethyl cellulose and, more particularly, these specific cellulose ethers present in a concentration within the range of about 1 to 5%, inclusive, by weight.

As specific examples of para-aminophenol developing agents for employment in the processing composition of the present invention, mention may be made of 2,3,6-trimethyl p aminophenol; 2,3,5-trimethyl-p-aminophenol; 2,3-dimethyl 6 methoxy-p-aminophenol; 2,6-dimethylp-aminophenol; 2-methoxy 6 methyl-p-aminophenol; 2-propoxy-p-aminophenol; 2,6-dimethoxy p aminophenol; 2-ethoxy 6 methyl-p-aminophenol; 2-methyl-6- propyl-p-aminophenol; 2-butoxy p aminophenol; 2- ethoxy-p-aminophenol; 2-methoxy p aminophenol; pmethylaminophenol; 4-benzylaminophenol; 2,4-diaminophenol; etc.

It will be recognized that the aforementioned silver halide developing agents may be employed in the form of their acid addition salts, such as the hydrochloride, where desired.

The p-arninophenol silver halide developing agent may be, and, with the exception of 2,3,6- and 2,3,5-trimethylp-aminophenols, preferably is employed in combination with additional silver halide developing agents, for example, preferably in combination with hydroquinone or one of its derivatives.

Silver halide solvents suitable for incorporation in the processing composition include conventional fixing agents such as sodium thiosulfate, sodium thiocyanate, ammonium thiosulfate, or associations of cyclic imides and nitrogenous bases such as associations of barbiturates or uracils and ammonia or amines. Of these, the coventional fixing agents specified are preferred and, most preferably, the solvent is present in a concentration within the range of about 0.3 to 20%, by weight.

Where desired, the processing composition may additionally include adjuncts known in the art such as restrainers, accelerators, preservatives, antifoggants, etc.

Homogeneous dispersion of relatively high concentrations of carbon black, for example, in the order of about 4% or more, by weight, may be facilitated by employment of conventional photographically inert surfactants. Such high concentrations of carbon black have also been specifically found to improve the transfer image characteristic curve shape, in addition to their opacifying action.

As previously noted, the print-receiving stratum preferably contains silver precipitating agents or nuclei, whose presence during the transfer process has a desirable effect on the amount and character of the silver precipitated during positive print formation. Examples of such silver precipitating agents are the metallic sulfides and selenides, thiooxalates, and thioacetamides, and colloidal metals disclosed in the aforementioned U.'S. Patent No. 2,698,- 237.

Referring now to the drawing, FIGURE 1 illustrates an assemblage and process of the present invention in the performance of a diffusion transfer process for the production of positive silver prints. As depicted in the drawing, an aqueous alkaline fluid layer 12, chosen in accordance with the present invention, is spread between photosensitive gelatino silver halide emulsion layer 11, which is affixed to opaque support 10, and silica image-receiving layer 13, which, as shown, is affixed to opaque support layer 14. Image-receiving layer 13 contains silver precipitating agents or nuclei, such as the silver precipitating nuclei previously mentioned as disclosed in U.S. Patent No. 2,698,237.

Under the circumstances, where a relatively high concentration of carbon black is present in the processing composition, and distribution of the composition between the superposed photosensitive and image-receptive elements is effected in the absence of incident radiation, further processing of the film unit may be accomplished in an environment containing such radiation in the absence of an opaque layer as a component of the reception element. In this circumstance the carbon black serves effectively to insulate the surface of photosensitive layer 11 opposite opaque support from additional photoexposure during such further processing.

Fluid layer 12 is obtained by distribution of the processing composition in a substantially uniform manner between photosensitive emulsion layer 11 and image-receiving layer 13, for example, in accordance with the procedures disclosed in US. Patent No. 2,543,181. For example, one or more rupturable containers retaining processing composition 12 may be attached to the photosensitive emulsion layer 11 and/ or image-receiving layer s 13 such that upon superposition of the respective layers 11 and 13 said container or containers are so positioned as to be capable, upon rupture, of releasing their contents in a substantially uniform layer between and in contact with the opposed surface of each of said layers. Rupture of the container or containers and spreading the contents thereof may be accomplished, for example, by compression between opposed, suitably gapped rollers.

In carrying out the aforementioned transfer process, the photosensitive emulsion 11 is exposed to a predetermined subject matter, to form therein a latent image of said subject matter. The exposed emulsion is superposed on image-receiving layer 13 and the photographic processing composition 12 spread between the opposed surface of said emulsion 11 and said image-receiving layer 13. The compositions reagents permeate into photosensitive emulsion 11, developing the latent image contained therein and forming a soluble silver complex of undeveloped silver. This soluble silver complex is transported from photosensitive emulsion layer 11, at least in part, by imbibition, to print-receiving layer 13 and the silver of the complex is precipitated thereat, to provide the desired positive image formation. The laminate, formed by the spreading of the processing composition as layer 12 between photosensitive emulsion layer 11 and print-receiving layer 13, is kept intact for approximately 10 seconds to one-half minute, preferably about 10 seconds, and at the termination of this time interval print-receiving layer 13 is dissociated from photosensitive emulsion 11 as, for example, by manual stripping.

The support layers designated in the drawing as 10 and 14 may comprise any of the various types of conventional opaque rigid or flexible supports, for example, paper, metal and polymeric films of both the synthetic types and those derived from naturally occurring products. It will be recognized that the opaque support layers will preferably be such as to prevent transmission of substantially all radiation to which wave lengths emulsion layer 11 is responsive, for example, substantially all incident ultraviolet and visible actinic radiation when layer 11 is a panchromatic emulsion, etc. It will also be further recognized that the opaque support may comprise a plurality of laminae, any one or more of which may be selectively opaque or transmissive and individually lack sufiicient dimensional stability to function as an independent support.

The photosensitive emulsion stratum may comprise a commercially available type silver halide gelatin emulsion such as the types sold by Eastman Kodak Company under the trade names Microfile, Spectrum Analysis, Contrast Process, SXX Aero Recon, Verichrome, Royal Pan, Royal X Pan, or Tri X Pan, or sold by E. I. du Pont under the trade names Fine Grain Pan, High Speed Pan, Arrow Pan, or Superior 3, or sold by Ansco under the trade name Triple S Pan, or sold by Gevaert under the trade name Gevapan.

While distribution of the processing composition in diffusion transfer processes has been described utilizing a frangible container, it will be apparent that said container provides a convenient means of distributing the liquid processing composition to permit the processing to be effected and that distribution of the composition may be otherwise effected where desired. It will also be apparent that processing may be totally effected Within the confines of a chamber insulating the film unit from incident radiation, for example, within such a chamber of a camera device.

The rupturable containers may be constructed in accordance with the disclosures set forth in US. Patent No. 2,634,886. The containers employed are, in general, constructed from a blank comprising a flexible, deformable, three-ply sheet material comprising, respectively, an outer layer of kraft paper, a layer of metal foil and an inner layer or liner of a thermoplastic resin, or two-ply sheet material comprising the latter two strata. The container blank is folded upon itself such as to provide a fluid-containing cavity and exhibiting a sealed passage adjacent to an edge thereof which may be substantially uniformly unsealed throughout a predetermined length of the sealed passage upon application of stress to the container.

The present invention will be illustrated in greater detail in conjunction with the following specific example which sets out representative employment of the processing compositions of this invention in silver diffusion transfer processes, which, however, are not limited to the details therein set forth and are intended to be illustrative only.

A plurality of photosensitive silver iodobromide emulsions mounted on paper base was exposed to a predetermined subject, advanced in superposed relationship with an image-receiving element comprising a siliceous imagereceptive stratum overcoated with a thin stripping layer comprising gum arabic (both the photosensitive and image-receiving elements comprise commercially available components of the general type sold by Polaroid Corporation, Cambridge, Mass, under the trade designation of type 47), between a pair of pressure-applying rollers to spread a processing composition comprising:

Sodium carboxymethyl cellulose g 305 Sodium sulfite g 50 Sodium thiosulfate g 108 6-nitrobenzimidazole g 2,4-diaminophenol g 319 Lithium hydroxide g 304 Carbon black g 400 Arabol cc 400 Water to make 9 liters.

between the photoexposed emulsion and the image-receiving element in a thin layer approximately 0.003 of an inch thick; [Arabol is a commercially available aqueous solution of gum arabic whose solid content varies between about 57% and 61% and which has viscosity varying between 1500 and 1700 centipoises]. After an imbibition period of about 60 seconds at room temperature, the emulsion, together with the layer of processing composition, was stripped from the image-receiving element of each film unit to uncover the positive prints.

For purposes of comparison, this procedure was repeated employing the processing composition described above except that the lithium hydroxide was replaced with 304 g. of sodium hydroxide.

The image-receiving elements of the film units processed with lithium hydroxide exhibited substantially complete separation from the layer of processing composition. The image-receiving elements processed with the sodium hydroxide processing compositions exhibited incomplete separation from the layer of processing composition, with portions thereof adhering to the surface of the separated image-receiving elements, particularly in the areas of transfer image silver precipitation. Similar experiments employing potassium hydroxide also resulted in portions of the layer of processing composition adhering to the surface of the image-receiving element. This problem increases as the processing temperature decreases.

The ability of the lithium hydroxide to prevent or at least substantially reduce the incidence of portions of the processing layer adhering to the surface of the imagereceiving element, when the photosensitive and imagereceiving elements are stripped apart, is particularly dramatic when the processing composition contains gum arabic and a stripping layer comprising gum arabic is coated over the image-receiving layer. Addition of gum arabic to the processing composition has been found to materially improve the stability of the dispersed carbon black.

In addition, it has also been found that where lithium hydroxide is employed, as above, in contradistinction to sodium or potassium hydroxide, the concentration of the p-aminophenol type developing agents necessary to provide comparative photographic sensitometry may be considerably less than that which would have been expected to be necessary to provide optimum photographic results employing sodium or potassium hydroxide.

This decrease in the concentration of the p-aminophenol silver halide developing agent improves the stability of the positive print, especially in the highlight areas of the transfer image, possibly, at least in part, by reduction of the incidence of oxidized developer and provides cleaner transfer image minimum densities, in addition to the favorable economics inherent in such a reduction.

Since certain changes may be made in the above products, processes and compositions without departing from the scope of the invention herein involved, it is intended that all matter contained in the above description or shown in the accompanying drawing shall be interpreted as illustrative and not in a limiting sense.

What is claimed is:

1. The photographic process which comprises the steps of exposing a photosensitive gelatino silver halide emulsion; developing exposed silver halide in said photosensitive emulsion with an aqueous solution, distributed intermediate said emulsion and a superposed print-receiving layer comprising a siliceous matrix containing silver precipitating agents, comprising, in combination, about:

1 to 7%, by weight, lithium hydroxide,

0.25 to 15%, by weight, carbon black,

1 to 8%, by weight, of a p-aminophenol silver halide developing agent, and

a silver halide solvent;

contacting undeveloped silver halide with said silver halide solvent and forming thereby an imagewise distribution of a soluble silver complex in the unexposed areas of said emulsion; transferring from said emulsion, at least in part, said imagewise distribution of said soluble silver complex to said print-receiving layer; precipitating said transferred silver complex to provide thereby a reversed positive silver print; and separating said print-receiving layer from its superposed relationship with said photosensitive emulsion subsequent to positive print formation.

2. The photographic process of claim 1 wherein said solution has a pH in excess of about .12.

3. The photographic process of claim 1 wherein said solution includes a viscosity increasing agent.

4. The photographic process of claim 3 wherein said viscosity increasing agent comprises hydroxyethyl cellulose present in a concentration within the range of about 1 to 5%, by weight.

5. A photographic composition which comprises an aqueous solution including, in combination, about:

1 to 7%, by weight, lithium hydroxide,

0.25 to 15%, by weight, carbon black,

1 to 8%, by weight, of a p-aminophenol silver halide developing agent, and

a silver halide solvent.

6. A photographic composition as defined in claim 5 wherein said solution has a pH in excess of about 12.

7. A photographic composition as defined in claim 5 wherein said solution includes a viscosity increasing agent.

8. A photographic composition as defined in claim 7 wherein said viscosity increasing agent comprises hydroxyethyl cellulose present in a concentration within the range of about 1 to 5%, by weight.

9. A photographic product which comprises, in combination, a photosensitive gelatino silver halide emulsion layer affixed one surface of a first opaque support, a siliceous print-receiving layer containing silver precipitating agents affixed one surface of a second support and adapted to be superposed on said emulsion layer, and a pressure-rupturable container retaining an aqueous solution comprising, in combination, about:

1 to 7%, by weight, lithium hydroxide,

9 0.25 to 15%, by weight, carbon black, 1 to 8%, by weight, of a p-aminophenol silver halide developing agent, and a silver halide solvent;

afiixed a leading edge of one of said emulsion and said print-receiving layers, adapted to be ruptured, upon application of pressure, and to distribute its contents intermediate said superposed emulsion and print-receiving. layers.

10. A photographic product as defined in claim 9 wherein said solution has a pH in excess of about 12.

11. A photographic product as defined in claim 9 Wherein said solution includes a viscosity increasing agent.

12. A photographic product as defined in claim 11 wherein said viscosity increasing agent comprises hydroxyethyl cellulose present in a concentration of from 1 to 5 by Weight.

13. A photographic product as defined in claim 9 wherein said solution includes gum arabic.

14. A photographic process as defined in claim 9 wherein a layer of gum arabic is affixed the surface of said print-receiving layer adapted to be superposed on said emulsion layer.

15. The photographic process which comprises the steps of exposing a photosensitive gelatino silver halide emulsion; developing exposed silver halide in said emulsion with an aqueous solution, distributed intermediate said emulsion and a superposed print-receiving layer comprising a siliceous matrix containing silver precipitating agents, 3

comprising, in combination, 1 to 7%, by weight, lithium hydroxide; 0. 25 to 15%, by Weight, carbon black; a silver halide developing agent; and a silver halide solvent; contacting undeveloped silver halide with said silver halide solvent and forming thereby an imagewise distribution of soluble silver complex in unexposed areas of said emulsion; transferring from said emulsion, at least in part, said imagewise distribution of said soluble silver complex to said print-receiving layer; precipitating said transferred silver complex to provide thereby a reversed positive silver print; and separating said print-receiving layer from its superposed relationship with said photosensitive emulsion subsequent to said positive print formation.

16. The photographic process of claim 15 wherein said solution includes gum arabic.

17. The photographic process of claim 15 wherein a layer of gum arabic is aflixed the opposed surface of said print-receiving layer.

18. A photographic developing composition which comprises an aqueous solution containing about 1 to 7%, by weight, lithium hydroxide; 0.25 to 15%, by Weight, carbon black; and a silver halide developing agent.

19. A photographic developing composition as defined in claim 18 wherein said solution includes gum arabic.

NORMAN G. TORCHI'N, Primary Examiner.

I. P. BRAMMER, Assistant Examiner. 

1. THE PHOTOGRAPHIC PROCESS WHICH COMPRISES THE STEPS OF EXPOSING A PHOTOSENSITIVE GELATINO SILVER HALIDE EMULSION; DEVELOPING EXPOSED A SILVER HALIDE IN SAID PHOTOSENSITIVE EMULSION WITH AN AQUEOUS SOLUTION, DISTRIBUTED INTERMEDIATE SAID EMULSION AND A SUPERPOSED PRINT-RECEIVING LAYER COMPRISING A SILICEOUS MATRIX CONTAINING SILVER PRECIPITATING AGENTS, COMPRISING, IN COMBINATION, ABOUT: 